Traditional pliers have, generally, two elongated members each having a handle at one end and a jaw at the other. The members cross over each other and are coupled by a pivot pin, or similar device, at a single, medial pivot in a manner similar to scissors. One enhancement to traditional pliers includes a dual pivot point on one member. That is, one member includes two pivot openings joined by a passage. The pivot pin is fixed to the other member. A user may then position the pivot pin in one of the two pivot openings. Further, the user may switch the location of the pivot point by moving the pin through the passage into the other pivot opening. In this configuration, the spacing of the jaws and the closing characteristics of the pliers may be changed.
A further enhancement includes elongating the dual pivot point to be a channel. The channel allows the two plier members to be placed in a number of configurations wherein the initial configuration of the jaws has the jaws spaced, adjacent to each other, or somewhere in between. The plier members are maintained in a specific relationship by a locking mechanism associated with a pivot member. One common locking mechanism is a tongue-and-groove arrangement wherein the plier member having the slot includes a series of arcuate channels disposed on either side of the groove, and, the other plier member includes a cam, i.e. a tongue, that may be selectively placed in a groove. Engagement of the cam in a groove creates a pivot point. Thus, the cam is the pivot member. Another locking mechanism is a rack-and-pawl arrangement. A rack-and-pawl arrangement includes a rack disposed in, or adjacent to, the groove. The plier member that does not include the rack has a pawl disposed thereon. When the pawl engages the rack, a pivot point is created. Thus, the pawl is the pivot member. Accordingly, with channel pliers, the closing of the jaws may include two motions; a sliding motion as a pivot member, e.g. the cam or the pawl, moves longitudinally relative to the groove, and, a pivoting motion after the pivot member is engaged.
Locking pliers have at least four primary members: a first member, that is a combined jaw/handle, a second jaw assembly, a second handle assembly, and one or more linking members. The second jaw assembly is pivotally coupled to the first member adjacent to the first member jaw so that the jaw members may close together. The second handle assembly is pivotally coupled to the second jaw assembly at a location spaced from the jaw member pivot point. The linking member extends between the first handle member and the second handle assembly. More specifically, the linking member extends from the distal end of the first handle member to a location adjacent to the pivot coupling of the second jaw and second handle assembly.
Thus, the first member jaw assembly and the second jaw may be moved between a first, open position and a second, closed position. The second handle and the linking member also move between respective first positions and second positions corresponding to the position of the jaws. When the components of the locking pliers are in their respective first positions, the pliers are in a first, open configuration. Similarly, when the components of the locking pliers are in their respective second positions, the pliers are in a second, closed configuration. The locking pliers typically have one or more springs structured to bias the locking pliers to the first configuration.
Locking pliers may have improved operational capabilities by reconfiguring the elements or adding additional links to provide for an enhanced closing motion. For example, in one improvement the second handle assembly may be coupled to the first member adjacent to the jaw, and, a second linking member extends from the second handle assembly to the second jaw. With this addition, the line of force acting on the second linking member/second jaw coupling is generally more tangent to the first member/second jaw pivot and, as such, enhances the force applied by the user when compared to the configuration identified above.
All such pliers, however, have a fixed jaw shape. That is, the jaw members of the pliers may have different shapes, e.g. a common arcuate shape, an elongated “needle nose” shape, or any other shape. Because the jaws are unitary, or otherwise fixed to, the plier handles, the shape of the jaws cannot be changed.
As shown in U.S. Pat. No. 4,813,310, attempts have been made to provide pliers with replaceable jaws. As shown in the '310 patent, a replaceable jaw member was attached to a lug disposed at the upper end of a plier member. The replaceable jaw member was structured to slide axially over the lug. In this configuration, i.e. when the mount and the replaceable jaw member had these shapes, there were no surfaces on the lug, or adjacent surfaces, that resisted the upward axial movement of the replaceable jaw member. That is, the replaceable jaw member was only maintained in its position by a latching member. Unfortunately, such latching members could not maintain the replaceable jaw member in a substantially fixed position. Thus, the replaceable jaw member would wobble on the lug. This is not a desirable configuration for pliers.